[cc/metrics] Fix trace-event for aborted frames.

If a 'begin main frame' is aborted (e.g. because of no visual damage),
then use the time of the abort as the termination time for the
trace-event, rather than when the reporter gets replaced by a new
reporter for the next frame, or when the scheduler drops the reporter
after the frame's deadline.

BUG=none

Change-Id: I4fdb32f8793eb7228439937759bdf12f0f3c0798
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2138963
Commit-Queue: Sadrul Chowdhury <sadrul@chromium.org>
Reviewed-by: Behdad Bakhshinategh <behdadb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#757979}

cc/metrics/compositor_frame_reporter.cc

@@ -224,6 +224,7 @@ CompositorFrameReporter::CopyReporterAtBeginImplStage() const {
       should_report_metrics_);
   new_reporter->did_finish_impl_frame_ = did_finish_impl_frame_;
   new_reporter->impl_frame_finish_time_ = impl_frame_finish_time_;
+  new_reporter->main_frame_abort_time_ = main_frame_abort_time_;
   new_reporter->current_stage_.stage_type =
       StageType::kBeginImplFrameToSendBeginMainFrame;
   new_reporter->current_stage_.start_time = stage_history_.front().start_time;
@@ -281,9 +282,8 @@ void CompositorFrameReporter::OnFinishImplFrame(base::TimeTicks timestamp) {
 }
 
 void CompositorFrameReporter::OnAbortBeginMainFrame(base::TimeTicks timestamp) {
-  DCHECK(!did_abort_main_frame_);
-
-  did_abort_main_frame_ = true;
+  DCHECK(!main_frame_abort_time_.has_value());
+  main_frame_abort_time_ = timestamp;
   impl_frame_finish_time_ = timestamp;
   // impl_frame_finish_time_ can be used for the end of BeginMain to Commit
   // stage

cc/metrics/compositor_frame_reporter.h

@@ -9,6 +9,7 @@
 #include <vector>
 
 #include "base/containers/flat_set.h"
+#include "base/optional.h"
 #include "base/time/time.h"
 #include "cc/base/base_export.h"
 #include "cc/cc_export.h"
@@ -151,12 +152,18 @@ class CC_EXPORT CompositorFrameReporter {
   void OnAbortBeginMainFrame(base::TimeTicks timestamp);
   void OnDidNotProduceFrame();
   bool did_finish_impl_frame() const { return did_finish_impl_frame_; }
-  bool did_abort_main_frame() const { return did_abort_main_frame_; }
   bool did_not_produce_frame() const { return did_not_produce_frame_; }
   base::TimeTicks impl_frame_finish_time() const {
     return impl_frame_finish_time_;
   }
 
+  bool did_abort_main_frame() const {
+    return main_frame_abort_time_.has_value();
+  }
+  base::TimeTicks main_frame_abort_time() const {
+    return *main_frame_abort_time_;
+  }
+
  private:
   void DroppedFrame();
   void MissedDeadlineFrame();
@@ -229,14 +236,14 @@ class CC_EXPORT CompositorFrameReporter {
 
   // Indicates if work on Impl frame is finished.
   bool did_finish_impl_frame_ = false;
-  // Indicates if main frame is aborted after begin.
-  bool did_abort_main_frame_ = false;
   // Flag indicating if DidNotProduceFrame is called for this reporter
   bool did_not_produce_frame_ = false;
   // The time that work on Impl frame is finished. It's only valid if the
   // reporter is in a stage other than begin impl frame.
   base::TimeTicks impl_frame_finish_time_;
   base::TimeTicks frame_deadline_;
+
+  base::Optional<base::TimeTicks> main_frame_abort_time_;
 };
 }  // namespace cc
 

cc/metrics/compositor_frame_reporting_controller.cc

@@ -312,13 +312,18 @@ void CompositorFrameReportingController::RemoveActiveTracker(
 void CompositorFrameReportingController::AdvanceReporterStage(
     PipelineStage start,
     PipelineStage target) {
-  if (reporters_[target]) {
+  auto& reporter = reporters_[target];
+  if (reporter) {
+    auto termination_time = (target == PipelineStage::kBeginMainFrame &&
+                             reporter->did_abort_main_frame())
+                                ? reporter->main_frame_abort_time()
+                                : Now();
     if (reporters_[target]->did_not_produce_frame())
       reporters_[target]->TerminateFrame(
-          FrameTerminationStatus::kDidNotProduceFrame, Now());
+          FrameTerminationStatus::kDidNotProduceFrame, termination_time);
     else
       reporters_[target]->TerminateFrame(
-          FrameTerminationStatus::kReplacedByNewReporter, Now());
+          FrameTerminationStatus::kReplacedByNewReporter, termination_time);
   }
   reporters_[target] = std::move(reporters_[start]);
 }